Washington (PTI): As developing countries confront the first global food crisis since the 1970s as well as unprecedented water scarcity, a new 53-city survey, including Bangalore and Chennai, conducted by the International Water Management Institute (IWMI) indicates that most of those studied are using untreated or partially treated wastewater for agriculture.

In over 70 per cent of the cities studied, more than half of urban agricultural land is irrigated with wastewater that is either raw or diluted in streams with wide ranging implications.

The conclusions of the study were released at 2008 World Water Week in Stockholm, and are based on data gathered from a diverse sample of developing country cities, chosen on the basis of factors such as water scarcity and income levels.

"Irrigating with wastewater isnt a rare practice limited to a few of the poorest countries," said IWMI researcher Liqa Raschid-Sally and lead author of a report on survey results.

"Its a widespread phenomenon, occurring on 20 million hectares across the developing world, especially in Asian countries, like China, India and Vietnam, but also around nearly every city of sub-Saharan Africa and in many Latin American cities as well."

Wastewater is most commonly used to produce vegetables and cereals (especially rice) and other IWMI reports, raising concerns about health risks for consumers, particularly of vegetables that are consumed uncooked. But at the same time, wastewater agriculture contributes significantly to urban food supplies and helps provide a livelihood for the urban poor, especially women, and recent migrants from the countryside,the IWMI has said in a Press Statement.